Demonstrators lie down along Pennsylvania Avenue in front of the White House during a protest against the proposed Keystone XL oil pipeline on March 2. / Manuel Balce Ceneta, AP

by David Jackson, USA TODAY

by David Jackson, USA TODAY

Police arrested dozens of opponents of the proposed Keystone XL oil pipeline on Sunday after they attached themselves to the White House gate.

Protesters who say the oil pipeline threatens the environment carried signs, such as "There is no planet B," and urged President Obama to veto the project that would run from Canada to the Gulf of Mexico.

The White House protest included about 1,000 people, some of whom wore white jumpsuits splattered with blank ink, meant to represent oil. They laid down on a tarp spread out on Pennsylvania Avenue as part of a symbolic oil spill.

"Canadian energy firm TransCanada Corp is behind the proposed pipeline that would carry crude from Alberta's oil sands to refineries on the U.S. Gulf Coast. Supporters say it would create thousands of jobs.

"The project already weathered a State Department environmental review, which was required because the project would cross international borders. Several other agencies also are doing reviews, and Obama has final say.

"Environmental groups, who fear oil spills along the pipeline and say it could hasten climate change, have staged a number of protests at the White House over Keystone."